Porous resilient printing plate



R. G. cHoLLAR 2,392,521 PORQUS RESILIENT PRINTING PLATE Janis, 1946.

Original Filed Feb. 12, 1942 Robert G. Chollar Inventor BY MM His Attorneyv latentedl Jan. 8, 1946 POROUS RESILIENT PRINTING PLATE Robert G. Chollar, Dayton, Ohio, assignor to The National Qash Register Company, Dayton, Ohio, a corporation of Maryland Original application February 12', 1942, Serial No. 430.661. Divided and this application April 1, 1943, Serial N0. 481,419

9 Claims. (GL 10i- 327) This' application is a division of my co-pending application Serial No. 430,681, filed February 12, now Patent No. 2,349,613, issued May 23,

This invention relates to resilient micro-porous printing plates and more particularly relates to such micro-porous resilient printing plates in which the resilient body acts asa reservoir and as a conductor for ink which is supplied to the type face through the pores. 1

It is known in the art of printing that porous printing members may be made of various materials .more or less hard in structure to be used to absorb and'conduct ink to a printing surface inscribed thereon. These porous substances have been non-resilient, so that printing qualities characteristic of a resilient surface equivalent to that of rubber could not be obtained.` Heretofore. an ink-resistant porous printing plate of suflicient strength for commercial use and of the fine surface porosity necessary to give even printing has not been produced.

'I'his invention relates to a printing member or plate made of porous rubber or rubber-like ma terial either of a single layer or of laminated structure, as will be described, said porous rubber and the process for making it being described in my co-pending application for United States Letters Patent Serial No. 427,326, filed on the nineteenth day of January, 1942, now Patent No. 2,353,877, issued on July 18, 1944.

The printing member which is the subject of this invention is a consolidated laminated member, the main body of which is coarsely microporous and the printing surface of which is nnely micro-porous, the two layers being bonded together in such a fashion that ink passes readily a printing member having a printing surface made of micro-porous rubber-like material which is supplied with ink through a coarsely micro-por- 'ous body structure by means of a wick-like structure. f

Another object of the invention is to provide a process for making the aforesaid objects.

With these and incidental objects in view, the invention includes certain novel features of construction and combinations of parts, the essential elements of which are set forth in appended claims and a preferred form or embodiment of which is hereinafter described with reference to the drawing which accompanies and forms a part of this specification.

In said drawing: 1 y

Fig. 1 is a cross-sectional view, in diagrammatic form, of the novel laminated resilient porous structure and means for supplying ink thereto.

Fig. 2 is a diagrammatical perspective view, partly broken away, of a typical porous resilient lamlnated'printing plate'and of the inking means therefor.

General description The laminated printing member ismade up' of a Vfinely porous layer I0 formed of particles of raw material passing a screen of less than 325 mesh to the inchin size,land of another layer Il, whichY is a coarser backing layer made up of particles of raw material passing a screen of from less than 25 to 100 mesh to the inch in size,

from one layer to another. Said coarser layer of the laminated structure is re-supplied with ink by means of a wick-like backing, which backing may be of porous metal, of woven fabric, of felted fiber, or of any other capillarilyconducting substance.

Therefore, the principal object of this invention is to provide a resilient micro-porous printing member.

Another object of the invention is to provide 2,353,877, to which reference has been made.y

as will be described. The two layers merge into one another at their juncture in such a fashion that the pores of one layer intercommunicate with the pores of the adjacent layer, so that whatever fluid recording material is contained in the layer Il is transmitted by capillary action to the layer ill. 'I'he porous layer I0, which forms the printing surface, is made with ne pores because it makes a more even impression, as the individ-` ual pores therein are not discernible by reason of the-mark deposited from the pore openings on recording material.

A method of making the porous rubber, although ladequately described in my Patent No.

will be summarized brieiiy herein.

Rubber or synthetic rubber finely comminuted to the proper mesh size, said. synthetic rubber being preferably of the butadiene co-polymer type, containing ordinary vulcanizing ingredients,

is mixed 55 parts by volumewith- 45 parts by volume of a finely comminutedller. One such mixture is made o f particles approximately less with mrticles apprommately less than the 25 to 100 mesh size. The ner mix is made into a uid mass;7 like a rubber cement, by the addition of a volatile solvent such as methyl-ethylketone and is applied to one surface of a Mom-inch thick water-soluble poly-vinyl alcohol sheet, said coatiing being made thick enough so that when dryit is apprommately 2%000 oan inch in thickness as a mammum. The poly-vinyl alcohol sheet with the coating thereon is placed in a die against a matrix of the printing surface to be formed, which matrix may be of Bakelite or other material that will withstand pressure and heat and will not adhere to the poly-vinyl alcohol. The uncoated side of the poly-vinyl alcohol sheet is placed next to the matrix. On top of this coating, preferably when dry, is placed the powder mix of the coarser variety so as to give the coarser layerv when molded, a maximum thickness of between 3%000 of an inch and 12%000 of an inch. The whole mass in the mold is compressed between the matrix and a ram with a'pressure of between 250 pounds to the square inch and 6000 pounds to the square inch, as the material requires, and then is vulcanized; The butadiene co-polymers require av temperature of about 307 degrees Fahrenheit for vulcanizing, which may be applied either in or out of the mold. The molded plate is removed from the mold, and the filler, which preferably is sodium nitrate, is dissolved outby washing in a solvent which has no effect upon the resilient asentar The use oi water-soluble poly=vinyl alcohol in the process described makes it possible to Wash material used. Sodium nitrate may be washed out with hot water containing a wetting agent, such as soap or one of the aliphatic penetrants. Other llers suggested are powdered metals, including powdered zinc; sodium carbonate; am-

monium sulphate; or powdered water-soluble poly-vinyl alcohol. Y

The sodium nitrate may be washed out of a. printing plate one-tenth of an inch thick in about two hours,|if it is agitated in hot water. The water in the pores after a Washing process is preferably replaced with ink by immersing the plate in ink above the boiling point of water, thus preventing possible adhesions of the pore surfaces. For the zinc, the carbonates, and the nitrates, acids may also be used, hydrochloric acid and dilute nitric acid being suggested. With the perto act as a strengthening support for the porous Y rubber and as a means to re-ink the porous rubber by means of a wick I3 inserted therein.

It is to be understood that the particular ma- "terials suggested are not to limit the scope of the invention.' The particular size lof the particles in the mix are specified as being best adapted for dye inks having an oil base. The butadiene `co-polymers are resistant to corrosion by such inks. The sodium nitrate is preferred as a. filler. as it may be washed out of the molded material with hot water, which will also dissolve any of thepoly-vinyl alcohol sheet that cannotbe removed by peeling. For other inks, for thicker plates, or for diierent molding temperatures, the

ingredients must be selected on the'basis 0l. their follow.

the poly-vinyl alcohol sheet on the molded mass as the ller is washed out to make the rubber pOlOllS.

The printing plate described is very compressible, and printing made from such a plate should be very light contact, which can be assured by surrounding the printing plate by non-resilient stops, preventing compression of the printing plate by contact with the record material. The supply of ink available at the type surface is vso copious that a light and fast contact is all that is necessary to make a well-defined impression. Therefore, the printing plate, not being subjected to severehammering and pressure, will last indefinitely as compared with ordinary printing plates, even though the porous structure is rather fragile as compared with solid printing plates.

It is obvious that the laminated structure shown may be used for filtering or for separatin g liquids or for separating solid material either in gases or in liquids, or'may be used for wicks for various purposes. The laminated structure for printing plates is, however, most important if fine printing is to be combined with high ink capacity and rapid recoveryv of the printing qualities after an'impression. The preferred embodiment described produces a, printing plate that will accommodate itself to impressions less than a secondapart for extended periods. i

While the product made in accordance with' .the process described herein is admirably adapted to fulfill the objects primarily stated, it is to be understood that the invention is directed particularly to the laminated structure. It is not intended to conne the invention to vthe preferred form or embodiment herein disclosed, for it is susceptible of embodimentin various forms by varying ingredients and processing steps, all coming within the scope of the claims` which What is claimed is: f

l. A. printing type consisting of a web of two joined layers of vulcanized micro-porousrubber saturated with ink, one of said, layers'being of finer porous structure than the other of said layers, the layer of finer porous structurehaving a printing surface consisting of printing characters, and the pores of each layer being interconnected and the pores of one layer connected to the pores y of the other layer to provide means for the ink to pass from one layer to the other and to the printing surface by capillary action.

2. An ink-saturated micro-porous rubber printbeing smaller than the pores in the back of said Sheet, the'larger pores acting as alreservoir and other laminated layer being formed together. and

the smaller pores acting to control the ow of ink to the printing surface.

4. A laminated printing type made of microporous rubber, formed of a layer of finely porous rubber having a surface thereof formed into a printing surface, and a layer of micro-porous rubber relatively coarse joined to said layer of finely porous rubber, the intercommunication of the pores from one layer to another being maintained.

5. A printing type formed of micro-porous rubber, having a printing surface consisting of a illm of very iine micro-porous rubber, which pores are communicative with the pores of the rest of the body, the pores of the said rest of the body being relatively coarser than the film.

6. A printingvmember consisting of a laminated micro-porous rubber structure,one of said laminations having smaller voids in the pore structure than the other, said one lamination being formed into relief to make printing'characters, and said ner laminated layer and' said a porous backing for said printing member.

7. A laminated structure ofporous material forming a printing type consisting of a backing llayer of relatively strong porous material, a middle layer consisting of porous and resilient rubber, and a printing layer consisting of fine microporous resilient rubber, al1 of'said members being bonded together and having their pores intercommunicating and saturated with ink.

8.v A printingtype made of a layer of vulcanized, resilient micro-porous butadiene co-polymer rubber backed by a porous structure of relatively greater strength, said rubber layer having printing *characters therein.

9. A printing type made of a layer of vulcanized resilient porous butadiene co-polymer rubber overlaid with a layer of the same material having a finer pore structure, and printing characters in said latter layer.

ROBERT G. CHOLLAR. 

